Translation:I work out every single day.
If you translate 每天, it refers to "every day". Because of 都 (numerical inclusive), there is no need to specify greater cardinal numbers (2, 3, ...). The point is to assume that the action is done every past period of time. Otherwise, the meaning of the sentence is vague, which then assumes that the event did not occur in some of all days.
Likewise, 都 should be included for "subtime" within a period of time, for instance,
Otherwise, the number is specified there, such as 每两天 (every two days). If this were to be included for the given translation, then we have
'I work out every two days.
However, because of 都, which makes every single day inclusive, this makes the sentence sound too redundant. Thus, the most accurate answer is
If 都 were to be excluded, then you are expressing that event occurred for some "pairs of days" (much like if you were to express 我每天锻炼).